NASA Reveals First Topographical Map of Saturn's Moon, Titan

Plastic is used in thousands of household items. But propylene, the chemical used to make food-storage containers, car bumpers and other products, isn't only found on Earth. NASA's Cassini spacecraft has also detected the material on Saturn's moon, Titan. Gemini North infrared image of Saturn and Titan (at about 6 o'clock position). (Photo : Gemini Observatory/AURA/Henry Roe, Lowell Observatory/Emily Schaller, Insitute for Astronomy, University of Hawai'i)

Orbiting Saturn is the massive moon, Titan. Now, NASA's Cassini spacecraft has peered through the thick orange clouds surrounding the moon in order to help create the first full topographical map of its surface using radar measurements.

Titan is Saturn's largest moon and is the second largest in the solar system right after Jupiter's Ganymede. Yet what makes Titan truly unusual isn't its size; it's the moon's unusual surface, including its ability to form clouds. The moon is the only one in the solar system with both clouds and a dense, planet-like atmosphere. It's surrounded by an orange haze that cloaks the surface and makes it hard to study.

Despite the difficulty in studying the moon, astronomers have been fascinated by Titan for years. In 2009, they actually captured an image of a storm on Titan. The astronomers had to employ advanced techniques to correct distortions caused by Earth's atmosphere. More specifically, they had to use adaptive optics, which use deformable mirrors to enable NSF's suite of ground-based telescopes to capture images that in some cases exceed the resolution of images captured by space-based counterparts.

"Adaptive optics are helping our ground-based telescopes accomplish feats that have until now been capable only with telescopes in space," said Brian Patten, a program director in NSF's Astronomy Division, in a news release. "Now, we can remove the effects of the atmosphere, capturing images that in some cases exceed the resolution of those captured by space-based telescopes."

Clouds aren't all that unusual on Titan--at least near the poles. There, clouds made up of light hydrocarbons rather than water emerge in the frigid, dense atmosphere where they feed scattered methane lakes below. Closer to the moon's equator, these clouds are rarer. The surface of Titan in these areas is more similar to an arid, wind-swept terrain on Earth.

Because these clouds are rare in the tropics, astronomers have been unable to explain liquid-carved terrain in the area. With the observations, though, researchers discovered the first storms ever seen near the moon's equator.

Now, scientists aren't just learning about its atmosphere. They're peering beneath the layers of clouds in order to examine Titan's surface. In order to do so, researchers used a mathematical process called splining - effectively using smooth, curved surfaces to "join" the areas between grids of existing data. This method added new layers to their studies of Titan's surface, especially those modeling how and where Titan's rivers flow, and the seasonal distribution of its methane rainfall.

The first thing that the researchers learned is that the moon is surprisingly flat--the topographical range of the moon's surface is just 1.5 miles. In addition to its flat surface, it seems that Titan's crust and geography are all composed of water ice instead of rock. Yet these aren't the only things the astronomers found. Cassini also revealed that Titan seems to bulge in the middle. In other words, the highest points on the moon's surface are at its equator, which explains why most of the moon's rivers flow toward the world's poles.

"Titan has so much interesting activity--like flowing liquids and moving sand dunes--but to understand these processes it's useful to know how the terrain slopes," said Ralph Lorenz, a member of the Cassini radar, in a news release. "It's especially helpful to those studying hydrology and modeling Titan's climate and weather, who need to know whether there is high ground or low ground driving their models."

So what does this new topographical map mean for studying Titan? The surface of a world can influence weather patterns, such as storms. With this new map, researchers are learning a little bit more about how the moon's surface influences weather patterns. The findings could also be applicable to other worlds in our solar system.